The pressure of a gas is the force exerted by the gas molecules on the walls of its container per unit area. It is measured in units of Pascals (Pa) or atmospheres (atm).
According to Boyle's Law, the pressure of a gas is inversely proportional to its volume at a constant temperature. This means that as the volume of a gas decreases, its pressure increases, and vice versa.
The pressure of a gas is affected by its temperature, volume, and the number of gas molecules present. An increase in temperature or number of gas molecules will result in an increase in pressure, while a decrease in volume will also lead to an increase in pressure.
The pressure of a gas can be measured using a device called a manometer or a pressure gauge. These instruments typically use a column of liquid to measure the pressure of the gas in units of height, which can then be converted to units of pressure.
When a gas is compressed, its volume decreases while the number of gas molecules remains constant. This results in an increase in pressure, as the gas molecules have less space to move around and collide with the walls of the container more frequently.